Add version guard to specs for OpenSSL::KDF.scrypt

[herwinw]

According to [1], this has been added in OpenSSL 3.0.

[1] https://www.openssl.org/docs/manmaster/man7/EVP_KDF-SCRYPT.html

This is a fix for an issue brought up in #1100.

[rhenium]

[1] https://www.openssl.org/docs/manmaster/man7/EVP_KDF-SCRYPT.html

This is the manpage for EVP_KDF, an entirely new set of API added in OpenSSL 3.0. ruby/openssl currently doesn't use it.

OpenSSL::KDF.scrypt (via EVP_PBE_scrypt()) works with OpenSSL >= 1.1.0. Also, LibreSSL doesn't support scrypt at all, so I think the guard has to be something like

!OpenSSL::OPENSSL_VERSION.include?("LibreSSL") && OpenSSL::OPENSSL_VERSION_NUMBER >= 0x10100000

[eregon]

We don't test against LibreSSL at all so I'm not worried about that for now.

Could you update the guard to use OpenSSL >= 1.1.0 then?